Article Abstract:
The measurement of grain-size in marine sediments reveals the changes in the relative strength of intermediate and deep currents in eastern North Atlantic Ocean during the past 25,000 years. This method of determining the changes in ocean current by measuring grain size is more reliable than the method which is based on the analysis of nutrient proxies in marine sediments. The study indicates that the water flow was rapid at depths ranging from 1,100 and 2,000 meters and that the deep water circulation was very slow during the last glaciation period. The slow movements in the deep region increased in strength after the glacial maximum.
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Article Abstract:
The early Archaean gneisses data of hafnium (Hf) and neodymium (Nd) isotopes suggest different concepts on early Earth differentiation of the crust and mantle. The Hf and Nd data predict an early loss of incompatible elements from the mantle because of crust extraction. However the data do not predict the scale and variability of the mantle depletion. The zircons of the rocks used for compositional analysis of Hf isotopes have larger amounts of Hf as compared to Nd. The Nd isotope data do not accurately record the isotopic changes in the early Earth.
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Article Abstract:
Neodymium isotope ratios are reported from dispersed Fe-Mn oxide in two southeast Atlantic sediment cores.
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